Evolving argument
Jerry Fodor and Massimo Piattelli-Palmarini discuss what they see as flaws in Darwin’s theory (6 February, p 28). They argue that Darwin, and his uncritical neo-Darwinian synthesis followers, got things wrong by attributing so much power to natural selection.
Their opinion piece covers two major themes: endogenous constraints and genetic free-riding. Darwin clearly acknowledged the first, and the neo-Darwinian synthesis has long accepted the latter. No sane evolutionary biologist would deny that evolution is time-constrained and that it must act on whatever designs are available at the time. So pigs could not evolve wings easily these days 鈥� big news.
Fodor and Piattelli-Palmarini argue that genetic linkage of phenotypic traits, in which one is selected and the other “free-rides”, are counter-examples to natural selection. That is just plain wrong. Linked phenotypic traits, or spandrels, can only free-ride for as long as they remain “silent”. If they ever decrease fitness in a significant manner and become a burden, natural selection will either lower the fitness of the linking trait, or select for individuals that happen to unlink both traits.
Ever since biologist Motoo Kimura popularised the concept of neutral evolution in the late 1960s, evolutionary biologists have widely accepted that natural selection is not the only factor in evolution. However, it still plays the leading role in the main evolutionary changes leading to the fundamental taxonomical differences observed between species.
From Ian Stewart
Judging by their arguments, Fodor and Piattelli-Palmarini seem to be aiming at the wrong target in entitling their book What Darwin Got Wrong.
The points they raise do not relate to flaws in the idea of natural selection, but to the many and varied constraints and influences under which it must operate. This has long been known: similar observations can be found in The Collapse of Chaos, which Jack Cohen and I wrote in 1994, as part of a critique of certain gene-centred aspects of neo-Darwinism.
The idea that natural selection involves a static measure of fitness influenced solely by the environment is naive and outdated. It is true that some models of evolution are restricted to these ingredients, particularly in classical population genetics, but few geneticists imagine that their models are complete descriptions of reality.
The transmission of genetic and epigenetic information to the next generation is a dynamic process: the fitness landscape changes in response to the evolving organisms, genes near to others can hitch a free ride, and what works is a compromise. All this is well known and has been for decades.
The issue is therefore not natural selection, but what this process involves and how it works. Darwin did not address these questions, and deserves no blame for the misconceptions of other people.
Warwick, UK
From Michael Crick
In discussing evolutionary pressure by “endogenous variables”, Fodor and Piattelli-Palmarini have put forward as new an idea about the evolutionary process that I thought was well understood.
The genome is part of nature and a source of pressure for selection. The first test for any new mutation is that it should be compatible with the existing genome. That the mutation need not be of benefit to the host is one reason for the redundant material accumulated by genomes. It is only after meeting this first requirement that the more obvious selection by external environmental factors becomes significant.
Darwin was unaware of the modern concept of the genome, but he was not wrong.
Hexham, Northumberland, UK
Aliens can't hear you
The comments by David Brin and others about broadcasting our presence to aliens leave me doubting the validity of the inverse square law governing the radio spectrum (13 February, p 24).
Applying this law shows that the combined output from all the radio stations on Earth is so diffuse as to be non-existent before it travels even one-millionth of the way to the nearest possible source of alien life, Proxima Centauri.
It seems likely, given the immense number of possibilities, that there is life on other planets in our galaxy, perhaps intelligent life on a few. However, having some grasp of the distances involved, one must realise the possibility of getting in touch is as near to zero as you can get.
Wonderful water
In his article on the unusual properties of water (6 February, p 32), Edwin Cartlidge failed to mention the weirdest property of all: the “Mpemba effect”. That is, if identical vessels of hot and cold water are placed in a freezer at the same time, the hot water will freeze first. This was first alluded to by Aristotle and then reported in the late 1960s as a result of observations by a young Tanzanian student. The findings were eventually published (), but the reason is still unexplained.
Code-breaking codon
In his article on horizontal gene transfer, Mark Buchanan erroneously states that the genetic code is “universal, shared by all organisms” (23 January, p 34).
In mammalian mitochondria there are two codes for methionine, rather than one, and one of the stop codons, which usually terminates a protein sequence, encodes tryptophan instead. In ciliated protozoans, two of the standard stop codons instead encode glutamine. Therefore the code is not universal, although it can be called widespread as, for example, the codon TCT codes for serine in any organism.
The editor writes
鈥� Joe Mortimer is correct. There are in fact numerous variations to the standard genetic code, particularly in mitochondria but also in the nuclear genomes of a few protozoans, algae and yeasts. These differences are presumed to have evolved after the fixing of the universal genetic code by horizontal gene transfer as discussed in our article, but we should have made their existence clear.
Darwin's conscious
Our yearning for distinction from the animal world induces us to explore some weird mental byways, one of which being that we are special because we possess consciousness (9 January, p 28, and 6 February, p 26).
This tedious hunt for distinction goes on because most people cannot quite believe the Darwinian proposition that we are, in fact, just animals. The biological facts are simple: we are animals in every sense and all our apparent distinctions are merely of degree, not of kind; a fact that is easier to spot if you turn off the cultural soundtrack and just watch the action.
Animals read the world via a series of sensory “snapshots”. We read our existence in exactly the same fashion, but our sensory snapshots are so multitudinous, overlaid and interlinked that the individual frames bleed together and run as a continuous movie in the multiscreen theatre of our overgrown brain, resulting in what we call consciousness.
Charles Darwin, 170 years ago, scribbled the following asides in his notes: “Thought, however unintelligible it may be, seems as much a function of organ, as bile of liver,” and “This view should teach one profound humility, no one deserves credit for anything, nor ought one to blame others.”
Sadly, this fact-based proposition is as unpalatable now as when Darwin originally noted it.
Quantum petunias
In your editorial on quantum biology, you write that “the pigments used in photosynthesis use quantum calculations” (6 February, p 5).
I shall soon be taking a closed-book exam and, since I suspect that most definitions of closed book would fail to make mention of pot plants, I intend take a plant into the exam with me, show it the questions and get it to do the appropriate calculations for me.
Since neither my gardening books nor BBC Radio’s Gardeners’ Question Time show have been of any help, are there any plants which you could recommend as being particularly adept in matters relating to the quantum universe?
Climate confusion
In his letter detailing why the Nobel committee rejected calls for new prize categories, Michael Sohlman claims that the Nobel prize in chemistry for 1995 was given to Paul Crutzen et al for work on “climate change” (13 February, p 22).
This prize was given for work on the ozone hole. This has little to do with climate change, although in the popular mind the two fields are frequently confused.
Weather isn't climate
Michael Payton criticises Michael Le Page’s suggestion that one cannot logically draw conclusions about climate change from a single severe weather event (6 February, p 27).
Payton appears to miss Le Page’s point entirely when he suggests that climate scientists are doing this by using extreme weather events as evidence of climate change. Le Page was not suggesting that one cannot make reasonable inferences about the climate from extreme weather, but rather that it is a statistical fallacy to draw conclusions about the climate from any single weather event or observation (16 January, p 20). After all, weather is not climate, but climate is the average of weather over a long period of time.
The fact that both sceptics and climate scientists are focusing on extreme weather events is irrelevant; the important point is that climate scientists recognise that robust and statistically significant conclusions about climate can only be drawn from the analysis of many weather events over a long period.
For the record
鈥� We lost our sense of proportion when stating how many people there are in the world without access to banking services who could benefit from mobile money technology. It is of course around a billion people, not a million as we stated (20 February, p 20).
鈥� In our article about atmospheric water vapour (6 February, p 16) we moved the University of Bern north of the border from its rightful location in Switzerland.
鈥� In a caption in our story on rock art, we noted that spiral signs on cave walls are rare. This was particularly the case for the picture in question, which actually depicted concentric circles (20 February, p 30).